Provided by the American Society for Microbiology
In recent years, evidence has
been building that injectable contraceptive depot medroxyprogesterone acetate
(Depo-Provera or DMPA) is associated with an increased risk of HIV infection.
Now a study published in the September 1st issue of mBio, an online open-access journal of the
American Society for Microbiology, provides a biological explanation for the
phenomenon. The findings will help women make more informed choices about birth
control.
"Before this study, there were all these controversial reports, some
showing that DMPA increases the risk of HIV infection and others showing it
doesn't, and there was no biologic explanation for the differences between
studies," said lead author Raina Fichorova, PhD, MD, director of the
Division of Genital Tract Biology at Brigham and Women’s Hospital and associate
professor of obstetrics and gynecology and reproductive biology at Harvard
Medical School, Boston. "This new study offers an explanation for the
inconsistent studies, and it lies in the microbial communities of the
reproductive tract."
The researchers analyzed cervical swabs and data from 823 women, between the
ages of 18 and 35, who were HIV negative and enrolled in family planning
clinics in Uganda and Zimbabwe. Roughly 200 women in this cohort became HIV
infected. Women were divided into three groups, those who used DMPA, those who
used estrogen-progesterone oral contraceptives, and those who used no hormonal
contraceptives. Within each of these groups, the investigators compared results
for women with a healthy vaginal environment (dominated by Lactobacillus-morphotypes
and free of bacterial vaginosis) to women who had a disturbed vaginal
microbiota or an infection from bacteria, fungi or parasites.
The team then looked to see if the women taking oral contraceptives or
receiving DMPA were more at risk for immunological changes that can increase a
person’s vulnerability to HIV infection than women who weren’t taking a
hormonal contraceptive. They found that DMPA use was associated with an
increase in these immunological changes, and that the presence of certain
vaginal infections further increased this risk. In addition, women who had
certain vaginal infections or disturbed resident microbiota and took oral
contraceptives were also at increased risk for this unfavorable, immunological
profile.
For example, women who had herpes and took DMPA, as well as women who had
herpes or disturbed vaginal microbiota and at the same time took
levonorgestrel-containing oral contraceptives, were more likely to have
increased levels of proteins that attract HIV host cells. This kind of inflammatory
response is implicated in increasing the risk of HIV infection, transmission,
or progression.
The research team also found that concurrent infections or disturbed vaginal
microbiota may also exacerbate the suppression of the immune system by DMPA,
thus adding to a woman’s vulnerability to HIV. For example, DMPA appeared to
suppress immune responses to Trichomonas
vaginalis, a wide-spread parasite that aids HIV infection.
"Women deserve to know more so that they can make informed choices about birth
control. Both men and women should be educated about our findings, as both
partners are at risk and need to prevent and treat infections," said Dr.
Fichorova. "Studies of new contraceptive methods should evaluate how they
impact the microbial environment and how they act in concert with preexisting,
treatable microbial disturbances, to weaken the mucosal barrier against HIV and
other infections. Our hope is to prevent the unwanted side effects of available
hormonal contraceptives and improve and save millions of lives by developing
new affordable tools and approaches to restore and keep the healthy vaginal
microbial environment in women of reproductive age."